Battery separators are widely used in liquid-electrolyte batteries to prevent physical contact between positive electrodes and negative electrodes within a given battery cell while simultaneously enabling ionic transport between electrodes. One type of battery separator is a porous or microporous polymeric separator. This type of separator is typically placed between the positive and negative electrodes within an electrochemical battery cell to physically isolate the electrodes from one another and to absorb liquid electrolyte into its porous structure. By being in intimate physical contact with each electrode, the separator containing the liquid electrolyte facilitates ion transport through the pores of the separator and between electrodes during the operation of the battery, either while discharging under an electrical load or while charging under an applied voltage from an external source.
Depending on the particular application for a liquid-electrolyte battery, any number of individual battery cells may be arranged in series, in parallel, or in various combinations thereof to satisfy the power requirements for the application. For example, a given battery cell is usually capable of producing a known voltage, based largely on the types of materials utilized, and has a particular current capacity, based largely on the materials utilized, the size of the components such as the electrodes and the surface area of the electrodes in contact with the electrolyte. To obtain the desired voltage from a battery, a sufficient number of individual cells are connected in series; e.g., six two-volt cells may be placed in series to obtain a twelve volt battery. To obtain the desired current capacity from the battery, multiple such sets of cells may be connected in parallel or multiple sets of cells connected in parallel may be connected in series. Of course other arrangements are possible.
In batteries that utilize multiple cells electrically connected to achieve usable power levels, one way that multiple electrodes of one polarity or the other can be connected to each another is via a common electrically conductive connection located along the same edge of each electrode. For example, individual electrodes sometimes each include a tab extending from a respective edge so that the multiple tabs of each polarity can be connected to one another by welding or some other suitable process to form an electrical connection between the individual electrodes. In some battery assemblies, such tabs extend from a top edge of each electrode or from a current collector associated therewith. Such internal battery connections may also be called internal terminals.
The inventors of the subject matter disclosed herein have recognized some potential problems that may result from battery constructions that include internal terminals such as those described above and have discovered structures and methods to help mitigate the problems.